Method and apparatus for screening corrosion inhibitors in boiler water



H. A. GRABOWSKI ETAL v 3,116,977 METHOD AND APPARATUS FOR SCREENINGcoRRosIoN Jan. 7, 1964 Filed Aug. 9, 1960 Fig. l.

INI/ENToRs Hilary A. Grubowski Peter F. Santen BY (2.1... ZZ@

TTORNE Y United States Patent METHD AND All ATUS FR S REENENG CllROSlNINHHBITRS iN BLER WAER Hilary A. Grahowsiri, Sinsliury, and Peter F.Santoro,

Thompsonviile, Conn., assigner-s to Combustion Engineering, inc.,Windsor, Conn., a corporation et lleiaware Filed Aug. 9, 196i?, Ser. No.@,471

Claims. (Cl. 231-230) This invention pertains generally to a method andapparatus for testinfy the electiveness of corrosion Water treatment orinhibitors and particularly for testing or screening corrosioninhibitors employed in the steam generating art.

It is the purpose of the invention to provide an apparatus and processfor testing a substantial number of specimens in a short time todetermine the eilectiveness of a corrosion inhibitor for use with steamgenerators under the conditions that prevail in the steam generator. Insteam enerators various inhibitors are employed to prevent or detercorrosion of the metallic parts of the steam generator and in theoperation of steam generators the conditions under which corrosion is aproblem include the intermittent wetting of the metallic tubes and otherelements in the evaporating region. In this region these metallicelements are intermittently wet and dry and as a result of theevaporating action concentrations oi boiler water constituents build upor accumulate on these elements.

The method and apparatus of the present invention provides a relativelysimple and effective way to duplicate, relatively accurately, theseoperating conditions and so test the effectiveness of the inhibitorsthat are dissolved in the boiling water to inhibit corrosion of theparts of the steam generator. The invention is particularly well adaptedto test the electiveness of water treatments or inhibitors to prevent orinhibit stress corrosion cracking of austenitic stainless steel employedwith steam generators particularly in the evaporating region. Thisproblem, with regard to stress corrosion cracking of this type ofmaterial, is an extremely serious one, with it having been found thataustenitic stainless steel, when under stress and disposed in boilerwater which contains chlorides, which all boiler Water does, is verysusceptible to this particular deterioration or corrosion.

In accordance with the invention there is provided a pressure containeror vessel which includes electric heating elements disposed about thevessel to heat water disposed therein and in which extends a rod whichis provided with a read at its end or inner extremity. A suitable motordrive is connected at the upper end of the rod to move the saine up anddown at a predetermined rate or period of reciprocation. The headcarries the specimens which are to be immersed in the boiler water thatcontains the particular inhibitor being tested and the lower region ofthis vessel contains this water with the water being heated by theaforementioned electric heaters 4to the desired temperature. The head ismoved up and down so as to raise and lower the specimens above and belowthe water level. Accordingly, the specimens are intermittently wetted.

lt is desirable to dry the specimens when they are located in the regionabove the water level so as to produce the evaporating effect in thesteamgenerator. Furthermore, since the action that takes place in asteam generator is to have the metallic elements heat the water or be ata higher temperature than the water such is the condition which prevailsin the organization of the invention. In order to heat the specimens,there is provided a source of electrical potential which is connected tothe specimen so as to pass a high current through them and arias??Patented dan. 7, ltl

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accordingly heat them Wherefore when the specimens are withdrawn fromand are above 'the liquid the liquid will quickly evaporate.

The head is designed so that a large number of specimens may be mountedthereon and accordingly a large number of specimens may besimultaneously tested and the operation of the organization is such thatthe conditions in the steam generator are closely duplicated and anaccurate and satisfactory test may be effected in a short time.

Accordingly, it is the object of this invention to provide an improvedmethod and apparatus for testing corrosion inhibitors as employed inboiler water and under the conditions existing in the steam generator.

Other and further objects of the invention will become apparent to thoseskilled in the art as the description proceeds.

With the aforementioned objects in View, the invention comprises anarrangement, construction and combination of the elements of theinventive organization in such a manner as 'to attain the resultsdesired as hereinafter more particularly set forth in the followingdetailed description of the invention as shown by the accompanyingdrawings wherein:

FlG. l is a somewhat diagrammatic representation of the organization ofthe invention with this representation being in the nature of a verticalsection;

FIG. 2 is a transverse section taken generally along line 2 2 of FIG. l;

FlG. 3 is a fragmentary sectional View through one portion oi the rimthat forms part of the head of the organization ot the invention.

Referring now to the drawing, wherein like reference characters are usedto designate like elements throughout, the illustrative and preferredembodiment of the invention depicted therein includes a pressure vesselor container l@ which is comprised of an inner cylindrical member 1?.,preferably made of Monel metal or the like, and provided at its upperend with threaded collar 14. Disposed about member l2 are a plurality ofelectric strip headers le which are connected with an electric potential13 through electric control device 2t). These heaters are effective toheat the boiler water 2l which partially lills vessel l@ with 22 beingthe level of this boiler water.

Disposed about cylindrical member l2 and heater elements ld is a layerof thermal insulation 24 with this insulation layer being containedwithin the shell or casing 26.

The upper end of vessel l@ is provided with a removable closure in 'theform of a threaded nut 25S which is threadably received on collar le andwhich is provided with a radially inwardly extending flange thatoverlays a complementary outwardly extending flange on the cover member3i? as disclosed. A iluid tight seal is provided by the gasket 32disposed intermediate cover member 3@ and the upper end of cylindricalmember l2.

Extending downwardly through and generally coaxial of cover member 3l)is the drive rod 343- and in order to insure a iiuid tight seal asuitable stuffing box 36 is provided which is secured to and extends upfrom member Sil as shown.

At the lower end of rod 34 there is mounted a head member 38 whichincludes a hub portion and a rim portion that is supported from the hub.This rim portion is of laminated construction as disclosed in FIG. 3 andincludes outer and inner metallic annuluses d@ and 42 respectively whichare separated by a layer of electrical insulation ed. The metallicspecimens are supported from this rim and the specimens are preferably Ubent as shown in FIG. 3, having their upper ends connected with theannuluses il and d2.

The head member 33 with its attached specimens is periodicallyreciprocated so that the specimens are moved up and down to and from aposition above the liquid level 2,2 and a position below the liquidlevel. This latter position being depicted in FiG. 1. In order toprovide this reciprocating action a suitable motor drive is connected tothe upper region of rod 3d with this drive, as illustrated, includingreversible electric motor lil which has connected with its shaft 42 apinion and with this pinion engaging suitable teeth le formed on the rod34. The operation of motor 4d is preferably controlled by timer 43 andthe resulting drive that is produced is eiective to maintain thespecimens in the position shown in FiG. l for a predetermined time, suchas live minutes, and thereafter elevate the specimens into a regionabove level 22 for another predetermined time, again such as fiveminutes, and continuously repeat this operation.

Each of the specimens 39 is heated by having a rela- 'tively highcurrent pass therethrough and for this purpose there is provided asource of electrical potential SG which is electrically connected withthese specimens by means of insulated conductors S2 and Srl that extendcentrally down through drive rod 34 with one of these connectors beingconnected with annulus d@ and the other with annulus 42. The potentialsource t? is of low voltage, high current capacity and is adjusted sothat the elements 39 will be heated to a temperature that is above thetemperature of the boiler water in vessel l0. For eX- ample the value ofthis potential source may be set to raise the temperature of thespecimens 16 to 20 above the temperature of the water while thespecimens are in the water phase and when the specimens are raised abovethe water level the temperature will increase because of the poorer heatdissipation qualities of steam as compared to water. When thus raised,the liquid adhering to the specimens will quickly evaporate.

At the beginning of a run, current will be supplied to the strip heaters16 and to the specimens 39, when the desired Water temperature isreached and which temperature is detected by the thermocouple 56 thestrip heaters 16 will be energized intermittently to maintain the watertemperature at its desired value while the specimens will be heatedcontinuously.

By forming specimens 39 in the manner disclosed the U bent portionthereof which is immersed intermittently in the body of water is, ofcourse, under stress as a result of bending the metal strip andaccordingly the effect of the inhibitor to prevent corrosion of thisstressed region will be determined.

It will be appreciated that a relatively large number of specimens canbe simultaneously tested, i.e. l2 to 18 and as previously mentioned, theorganization is well adapted for testing the effectiveness of chloridestress corrosion Water treatments. in testing these treatments orinhibitors the specimens 39 would be austenitic stainless steel ofvarious types and make ups and the production of stress corrosion cracksat the stressed U bend portions of the specimens would be determinedwith this determination representing the actual conditions prevailing inthe steam generating region of a boiler.

Accordingly a relatively simple, yet eitective method and apparatus isprovided in accordance with the invention for screening corrosioninhibitors for use in the boiler Water of steam generators.

While we have illustrated and described a preferred embodiment of ourinvention, it is to be understood that such is merely illustrative andnot restrictive and that variations and modifications may be madetherein without departing from the spirit and scope of the invention. Wetherefore d0 .1,101 Wish to be limited to the precise details 4 setforth but desire to avail ourselves of such changes as tall within thepurview of our invention.

What is claimed is:

1. The process of screening corrosion inhibitors for boiler watercomprising providing in an enclosed container a heated bath of waterhaving the inhibitor dissolved therein, periodically immersing aplurality of metallic test specimens into the bath and withdrawing thesame into the space thereabove, passing a current through said specimensand thereby heating the same to a temperature above said bath and so thespecimens quickly become dry when moved from the Water bath into saidspace, and continuing the periodic emersion and withdrawal for asubstantial period.

2. The process of testing the effectiveness of inhibitors of stresscorrosion cracking of austenitic stainless steel in boiler watercomprising providing a heated bath or" boiler water having the inhibitordissolved therein, provid-.ing a bent specimen of austeniticstainlesssteel so that stresses are developed at said bend, for apredetermined time, pcriodically immersing the bent portion or" thespecimen in said bath and withdrawing the same into the space andpassing a current through said specimen to heat the same to atemperature above said bath and so it will quickly become dry when movedfrom the water bath into said space.

3. An organization of the type described comprising a generally tluidtight vessel partially iilled with boiler water having a corrosioninhibitor dissolved therein, means for heating said water to a desiredtemperature, means operative to support a metal specimen in said vesseland periodically move the same into and out of said water, a source ofelectric potential and means connecting said source to said specimen soas to pass current therethrough, said source being such as to heat saidspecimen to a desired temperature above the temperature of the water.

4. A device for testing the effectiveness of a stress corrosion crackinginhibitor in boiler water comprising a pressure vessel partially iilledwith boiler water having said inhibitor dissolved therein, support meansexten(- ing through the upper end of the vessel, a plurality of bentstrips of austenitic stainless steel supported by said means within saidcontainer, means operative to periodically move said support to move thebent portion of the strips into and out of the water, a source ofelectric potential connected with said strips to pass currenttherethrough, said source being such as to heat said specimen to a'desired temperature above the temperature of the water.

5. Testing apparatus for testing the effectiveness of corrosioninhibitors in boiler water comprising a pressure vessel, partiallyfilled with boiler water having the inhibitor dissolved therein,electric heater means disposed about the vessel to heat the watertherein, a vertically disposed shaft extending through the upper end ofthe vessel in a generally fluid tight manner, a head secured to thelower end of the shaft, a plurality of metal specimens supported on saidhead for periodic immersion in the water, motor means connected with theupper end of the shaft and operative to periodically reciprocate thesame to effect said periodic immersion, a source of electric potential,means connecting this source with said specimens to pass currenttherethrough, said source being such that the specimens are heated to atemperature above that of the water.

References Cited in the file of this patent UNITED STATES PATENTS2,405,52 Todd Aug. 6, 194s

1. THE PROCESS OF SCREENING CARROSION INHIBITORS FOR BOILER WATERCOMPRISING PROVIDING IN AN ENCLOSED CONTAINER A HEATED BATH OF WATERHAVING THE INHIBITOR DISSOLVED THEREIN, PERIODALLY IMMERSING A PLURALITYOF METALLIC TEST SPECIMENS INTO THE BATH AND WITHDRAWING THE SAME INTOTHE SPACE THEREABOVE, PASSING A CURRENT THROUGH SAID SPECIMENS ANDTHEREBY HEATING THE SAME TO A TEMPERATURE ABOVE SAID BATH AND SO THESPECIMENS QUICKLY BECOME DRY WHEN MOVED FROM THE WATER BATH INTO SAIDSPACE, AND CONTINUING THE PERIODIC EMERSION AND WITHDRAWAL FOR ASUBSTANTIAL PERIOD.